Small Bodied Humans From Palau

Palau is fast becoming an anthropological paradise. In addition to being one of the places Margaret Mead did fieldwork, we now have news that a large collection of skeletons have been found. Currently, the fragmentary remains of 25 individuals have been excavated, but others remain to be freed from their calcium carbonate matrix:


Palau

Picture Source
Let’s start at the beginning. The find is being published in PLoS One. The material was found in two caves (Ucheliungs and Omedokel) which are not, apparently habitation areas. Material in the first cave dates, via AMS, to 1420-2890 years BP, while material from the second cave dates to 1410-2300 years BP. The skeletal material is, apparently, the result of secondary deposition rather than primary burials. The intriguing part is the size of the skeletal material. For example, a left os coxa (belonging to a female) is similar in size to AL-288-1 (Lucy), several others (males) are similar in size to the LB1 os coxa. Measurements of the acetabulum (the socket where the head of the femur articulates with the pelvis) allowed body mass to be estimated (28.7 kg for the female, 43.2 kg for one male). Measurements on the femur, tibia, and talus provided similar body size estimates. Several were also similar in size to LB1. The authors summarize this section by noting:

More than 61 measurable postcranial elements recovered from the two caves also indicate body sizes at the lower extreme of recent human variation and in some cases the range of smallbodied australopithecines. These include tali that approach closely the size of the talus of the small bodied australopithecine ”Little Foot” from South Africa (Figure 6), supporting the hypothesis that small body size was the norm in the earlier populations preserved in the cave.

If you are jumping to some conclusions right about now, like “hey, didn’t someone float the idea that Homo floresiensis evolved from australopithecines” you should probably stop.
Earlier in the paper the authors describe a number of traits autapomorphic for Homo sapiens. These traits include a maxillary canine fossa, mandibular mental trigone, bossing on the frontal and parietal among others.
On the other hand, the new finds do share some traits with the Flores finds. Among them are reduction of the craniofacial area, megodontia, some had suprorbital tori, weakly developed or absent mental fossae and mental tuburcles, and rotated or missing teeth. Brain size is larger than in LB1, but is within range of Homo erectus and at the lower end of H. sapiens
So, we have an intriguing mix of morphology. What do the authors make of it? After cautioning that the traits linking H. erectus, H. floresiensis, and the Palau population could be homoplasies (early in the paper) the authors make an excellent point when they observe that small bodied populations that do not share all the traits considered taxonomically significant in the LB1 material can not support the validity of the H. floresiensis taxon. They conclude the paper by saying:

Based on the evidence from Palau, we hypothesize that reduction in the size of the face and chin, large dental size and other features noted here may in some cases be correlates of extreme body size reduction in H. sapiens. These features when seen in Flores may be best explained as correlates of small body size in an island adaptation, regardless of taxonomic affinity. Under any circumstances the Palauan sample supports at least the possibility that the Flores hominins are simply an island adapted population of H. sapiens, perhaps with some individuals expressing congenital abnormalities.

Which prompts me to ask if anyone has ever considered what a population of H. erectus that had been subject to island dwarfing would look like. Most of the debate that I am aware of, and someone please correct me if I’m wrong, uses H. sapiens as a starting point.

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21 Responses

  1. That’s an interesting question. I don’t know the answer myself, but I’d be fascinated to know if anyone else does.

  2. I know, it’s a low resolution image, but that skull looks rather modern. Domed, high forehead; in all about what you’d expect form a small adult Homo sopiens. I suspect there’s more to this story than what we’ve heard so far.

  3. Size reductions are reasonably common in island and tropical forest-dwelling species although I recall a recent paper claiming this was not invariably so. But the Mediterranean Islands, for example, provide many examples. Seems to me it is not impossible that the Palau fossils are size-reduced H. sapiens and the Flores specimens are size-reduced H. erectus, or something between erectus and sapiens in the latter case. Whether or not we classify any of them as separate species depends entirely on one’s definition of ‘species’.

  4. OK, seriously ignorant question. How much morphological change/reproductive isolation would be required for a dwarf island population of species X to be regarded as a separate species Y?

  5. It appears that small people have lived in SE Asia for a long time:
    http://www.cwo.com/~lucumi/filipinos.html
    Disclaimer: I picked that link from a Slashdot comment. As a whole those pages seem to be politically motivated, but at least the writer provides references.

  6. It appears that small people have lived in SE Asia for a long time:
    http://www.cwo.com/~lucumi/filipinos.html
    Disclaimer: I picked that link from a Slashdot comment. As a whole those pages seem to be politically motivated, but at least the writer provides references.

  7. It appears that small people have lived in SE Asia for a long time:
    http://www.cwo.com/~lucumi/filipinos.html
    Disclaimer: I picked that link from a Slashdot comment. As a whole those pages seem to be politically motivated, but at least the writer provides references.

  8. I’m a layman with a lifelong interest in paleoanthropology (50 years), but quite limited knowledge in such technical fields as comparative anatomy and physiology. With that substantial caveat, the initial information available about the Palau finds suggests the possibility they may eventually aid the establishment of the H.floresiensis taxon. For example, one of the issues raised about the island dwarfing hypothesis regarding H. f. questioned whether such dwarfing would result in a reduction in cranial size as drastic as that seen in H.f. The crania from the Palau specimens (H. sapiens) are reduced to below 1000 cc, which is not grossly inconsistent with the crainial reduction in H.f., assuming a homo erectus ancestry for H.f.

  9. I’m a layman with a lifelong interest in paleoanthropology (50 years), but quite limited knowledge in such technical fields as comparative anatomy and physiology. With that substantial caveat, the initial information available about the Palau finds suggests the possibility they may eventually aid the establishment of the H.floresiensis taxon. For example, one of the issues raised about the island dwarfing hypothesis regarding H. f. questioned whether such dwarfing would result in a reduction in cranial size as drastic as that seen in H.f. The crania from the Palau specimens (H. sapiens) are reduced to below 1000 cc, which is not grossly inconsistent with the crainial reduction in H.f., assuming a homo erectus ancestry for H.f.

  10. Chris asked, “How much morphological change/reproductive isolation would be required for a dwarf island population of species X to be regarded as a separate species Y?”
    That’s the problem. Officially we would regard them as separate species if they were unable to produce fertile offspring. But how do we test that? Dwarfism doesn’t necessarily indicate speciation. Pygmy Africans for example have no trouble forming fertile offspring with what we might refer to as ‘normal-sized’ people. DNA evidence may go some way to solving the problem in this case but there’s no guarantee at all that any survives in the fossils.
    And of course I’d personally love to discover a new species. Perhaps we’re too ready to classify new finds as new species.

  11. T.R.
    I think you are completely correct in that this actually supports island dwarfing forming such a low cranial capacity.
    Funnily enough the authors here seem to view this as the death knell of H. floresiensis, whereas I think it explains the most difficult to understand aspect of the flores hominin.
    When you consider the wrist data of H.floresiensis it simply could not have been a H. sapiens.

  12. My opinion, from a paleobiologist’s perpective, on the Berger et al. paper:
    It is clear that the palau fossils are a very interesting new form, indeed probably a new species of Homo. However, much controversy has yet to be cleared away.
    Berger et al. state as “plain fact” that these tiny Palauans are descended from H. sapiens. This is an affirmation about the phylogenetic relationships of this new fossil form. This affirmation may seem at odds with some primitive traits of this new form, as well as traits exclusively shared with H. floresiensis. These traits are dismissed by Berger et al as taxonomically insignificant convergences and reversions, such as could be produced by an epigenetic correlate of small body size.
    However, without a phylogenetic analysis, Berger hasn’t really presented the evidence to justify his affirmation that these tiny Palauans are H. sapiens. In fact, a mix of human autapomorphies and primitive traits suggest a species that may be closely related to H. sapiens, sharing many traits, yet still diverged previous to modern H sapiens (such as Palauans) that lack these primitive traits.
    To discard this possibility and prove that tiny Palauans are H. sapiens, Berger et al. would have had to show that their tiny Palauans are phylogenetically nested within H. sapiens. However they did not make a phylogenetic analysis (despite disposing of several specimens and good morphological data)
    Without that, they are simply preferring hypotheses of convergence or reversal rather than homology for the primitive traits, which is, in fact, contra-parsimony as an initial assumption.
    A little PAUP on the morphological traits has become almost a standard procedure in systematics and paleontology when describing a new fossil form with evolutionary relevance.
    Statements such as “We feel that the most parsimonious, and most reasonable, interpretation of the human fossil assemblage from Palau is that they derive from a small-bodied population of H. sapiens” are not acceptable as a substitute for actual phylogenetic analysis using parsimony. If Berger et al did that analysis, they would KNOW, rather than FEEL, whether the affirmation “tiny palauans are H. sapiens” indeed stands out as the most parsimonious hypothesis.

  13. I think phylogenetic analysis may very well confirm, that H. sapiens is not the starting point for Palau man, as you guys say.

  14. I think phylogenetic analysis may very well confirm, that H. sapiens is not the starting point for Palau man, as you guys say.

  15. There is good evidence that Homo erectus was not the only, and not even the first, hominin in SE Asia. The impoverished, basically Oldowan tool industry at the most ancient sites there suggest strongly that the earliest humans there were representatives of Homo habilis, not Homo ergaster or Homo erectus. If this is indeed the case, then efforts to derive these pygmy populations from H. sapiens may be both misguided and doomed to lead to irreconcilable problems. Do we really know how long it takes an island location to produce dwarfing? Is the shallow presence of Homo sapiens in SE Asia long enough for this to have happened? In my opinion, the most reasonable thing to do is to establish these two populations as a new taxon (or two new taxa), and then try to work backwards to a different progenitor species. Since the dates for these new finds are not at all ancient, resemblances to modern humans could come from interbreeding with moderns, couldn’t they?

  16. In my earlier post I forgot to mention that the Dmanisi hominin is also quite small, and very possibly a continental form of the same “race” as the SE Asian island hominins. Regarding the very old primitive tool industries of Southeast Asia, Movius (and others) were never able to account for it; Movius even suggested that the makers were mentally challenged! Why it has not been related to the Oldowan tradition is really puzzling to me.

  17. I admittedly know nothing about this topic, but what evidence is there that these smaller skeletons are mature, fully grown examples of the species? Could these be the bones of children who died in an epidemic? Or could there have been a high incidence of dwarfism in an otherwise larger population size?

  18. That is a good question. according to the paper they recovered both subadult and adult material. There are a number of methods to determine age; epiphyseal union, cranial suture closure, eruption of the teeth, age changes in the pubic symphysis, and age changes in the area where the sacrum articulates with the ilium, are some that immediately spring to mind.

  19. That is a good question. according to the paper they recovered both subadult and adult material. There are a number of methods to determine age; epiphyseal union, cranial suture closure, eruption of the teeth, age changes in the pubic symphysis, and age changes in the area where the sacrum articulates with the ilium, are some that immediately spring to mind.

  20. DNA results reveal the skull is a distant relative of Dennis Kuciich!

  21. A few years ago I was in a group of women on a dogsled trip above the Arctic Circle in Norway. Our guide for a five-day trek was a well-educated Norwegian who said seriously that there are “little people”living in deep caves in Norway. He specified these are not trolls, gnomes, or the like; but simply very small people (smaller than the Sami of the region) who are sly and sometimes play tricks on humans. Now it makes me wonder–

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